共查询到20条相似文献,搜索用时 0 毫秒
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We develop “perturbation theory” rules for calculating the effect of instantons in a pure Yang-Mills theory with no fermions, in the “dilute gas” approximation in which the N-instanton solution is assumed to be the sum of N widely separated one-instanton solutions. These rules are then used to compute the gluon propagator and proper vertex function including all orders of the instanton interaction but only to lowest order in the gluon coupling. It is to be expected that such an approximation is valid only for momenta q larger than the physical mass μ. The result is that in this regime instantons cause variations in the propagator and vertex of the form where b is the coefficient in the expansion of the β function: β = bg3 + 3. . 相似文献
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Sorna Prava Barik Kamal L. Panigrahi Manoranjan Samal 《The European Physical Journal C - Particles and Fields》2018,78(11):882
We discuss semiclassical quantization of circular pulsating strings in \( \text {AdS}_3 \times \text {S}^3 \) background with and without the Neveu-Schwarz–Neveu-Schwarz (NS–NS) flux. We find the equations of motion corresponding to the quadratic action in bosonic sector in terms of scalar quantities and invariants of the geometry. The general equations for studying physical perturbations along the string in an arbitrary curved spacetime are written down using covariant formalism. We discuss the stability of these string configurations by studying the solutions of the linearized perturbed equations of motion. 相似文献
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David M. A. Stuart 《Communications in Mathematical Physics》1992,149(3):433-462
In this paper we prove the validity of formal asymptotic results on perturbation theory for kind solutions of the sine-Gordon equation, originally obtained by McLaughlin and Scott. We prove that for appropriate perturbations, of size in an appropriate norm, slowly varying in time in the rest frame of the kink, the shape of the kink is unaltered in theL
norm toO() for a time ofO(1/). The kink parameters, which represent its velocity and centre, evolve slowly in time in the way predicted by the asymptotics. The method of proof uses an orthogonal decomposition of the solution into an oscillatory part and a one-dimensional zero-mode term. The slow evolution of the kink parameters is chosen so as to suppress secular evolution of the zero-mode.Partially supported as a graduate student at Princeton University of NSF grant 215 6211 相似文献
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Using the basic ingredient of supersymmetry, a simple alternative approach is developed to perturbation theory in one-dimensional non-relativistic quantum mechanics. The formulae for the energy shifts and wavefunctions do not involve tedious calculations which appear in the available perturbation theories. The model applicable in the same form to both the ground state and excited bound states, unlike the recently introduced supersymmetric perturbation technique which, together with other approaches based on logarithmic perturbation theory, are involved within the more general framework of the present formalism. 相似文献
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This paper studies the perturbation of soliton due to the chiral nonlinear Schrödinger's equation by the aid of soliton perturbation theory. The perturbation term that is studied is the quantum potential perturbation of the chiral soliton that is known as Bohm potential. The stable fixed point of the chiral soliton parameters is obtained. 相似文献
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Let A be a densely defined symmetric operator and let {Ã′, Ã} be an ordered pair of proper extensions of A such that their resolvent difference is of trace class. We study the perturbation determinant ΔÃ′/Ã(·) of the singular pair {Ã′, Ã} by using the boundary triplet approach. We show that, under additional mild assumptions on {Ã′, Ã, the perturbation determinant ΔÃ′/Ã(·) is the ratio of two ordinary determinants involving the Weyl function and boundary operators. In particular, if the deficiency indices of A are finite, then we obtain ΔÃ′/Ã(z) = det (B′ - M(z))/det (B - M (z)), z ∈ ρ(Ã), where M(·) stands for the Weyl function and B′ and B for the boundary operators corresponding to Ã′ and à with respect to a chosen boundary triplet Π. The results are applied to ordinary differential operators and to second-order elliptic operators. 相似文献
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M. E. Gorbunov 《Radiophysics and Quantum Electronics》1995,38(7):438-443
Perturbation theories for the rays and for the eikonal are discussed. It is shown that these theories give completely equivalent results in the calculation of any arbitrarily chosen value. The problem of refraction in an arbitrary inhomogeneous medium is considered as an example.Institute of Physics of Atmosphere, Fryazino, Moscow region. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 7, pp. 660–667, July, 1995. 相似文献
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We study the decays K→ππ in one-loop two-flavour Chiral Perturbation Theory. We provide arguments why the calculation of the coefficient of the pionic chiral logarithm ℓM=M2logM2 is unique and then perform the calculation. As a check we perform the reduction of the known three-flavour result. Our result can be used to perform the extrapolation to the physical pion mass of direct lattice QCD calculations of K→ππ at fixed ms or . The underlying arguments are expected to be valid for heavier particles and other processes as well. 相似文献
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Z. Sedláček 《Czechoslovak Journal of Physics》1968,18(5):618-628
It is shown that the complete spectrum, continuous as well as discrete, and corresponding eigenfunctions of the Vlasov operator can be obtained by a single perturbation procedure from the purely continuous spectrum and corresponding eigenfunctions of the free-streaming operator. In addition we present an alternative definition of the eigenfunctions and show that the problem of normalizing the continuous eigenmodes is thus solved automatically. 相似文献
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M.I. Jaghoub 《The European Physical Journal A - Hadrons and Nuclei》2002,15(4):443-448
In the presence of a velocity-dependent Kisslinger potential, the partial-wave, time-independent Schr?dinger equation with
real boundary conditions is written as an equation for the probability density. The changes in the bound-state energy eigenvalues
due to the addition of small perturbations in the local as well as the Kisslinger potentials are determined up to second order
in the perturbation. These changes are determined purely in terms of the unperturbed probability density, the perturbing local
potential, as well as the Kisslinger perturbing potential and its gradient. The dependence on the gradient of the Kisslinger
potential stresses the importance of a diffuse edge in nuclei. Two explicit examples are presented to examine the validity
of the perturbation formulas. The first assumes each of the local and velocity-dependent parts of the potential to be a finite
square well. In the second example, the velocity-dependent potential takes the form of a harmonic oscillator. In both cases
the energy eigenvalues are determined exactly and then by using perturbation theory. The agreement between the exact energy
eigenvalues and those obtained by perturbation theory is very satisfactory.
Received: 24 May 2002 / Accepted: 15 July 2002 / Published online: 3 December 2002
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ID="a"e-mail: mij@hu.edu.jo
Communicated by V. Vento 相似文献
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We explore the possibility of formulating a consistent time-dependent perturbation scheme in Bohmian mechanics as a (necessary?) prerequisite to construct a Bohmian radiation theory. Difficulties are outlined and also illustrated numerically. Particular attention is given to the first order perturbation of a one dimensional harmonic oscillator by an electric dipole interaction which allows for an analytic solution for the particle trajectory independently from the details of the unperturbed wave function. 相似文献
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A. A. Kostarev 《Russian Physics Journal》1965,8(1):90-92
Perturbation theory of the inverse problem is discussed for a certain class of S-matrices. The convergence of the perturbation series is proved for this class. 相似文献
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O. Steinmann 《Communications in Mathematical Physics》1993,152(3):627-645
A perturbative expansion of the Wightman functions, and more generally of vacuum expectation values of products of time-ordered and anti-time-ordered products, is derived for
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field theory. The result is expressed as a sum over generalized Feynman graphs. The derivation is based exclusively on the equation of motion and the Wightman axioms. Neither canonical commutation relations nor asymptotic conditions are needed at any point. In the zero-mass case the individual graphs are infrared divergent, but the sum over all graphs of a given order is convergent. 相似文献
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《Physics letters. A》1987,125(9):443-446
A new version of the Rayleigh-Schrödinger type of perturbation theory is presented. It is based on a rearrangement of hamiltonians H=T+λV containing a non-diagonal (band-matrix, strong-coupling) zero-order component T. Its efficiency is illustrated on the anharmonic oscillator. 相似文献